Tamar Bridge
 |
The Tamar Bridge during widening and strengthening work, 1999 |
The
Tamar Bridge is a major
road bridge in
southwest England carrying traffic between
Devon and
Cornwall. When it opened in
1961 it was the longest
suspension bridge in the
United Kingdom. In
2001 it became the world's first suspension bridge to be widened (from three to five lanes) using
cantilevers, and the world's first bridge to undergo strengthening and widening work while remaining open to traffic. The five lanes are divided as follows: three lanes carry the
A38 trunk road, the fourth is reserved for eastbound local traffic and the fifth for
pedestrians and
cyclists. Previously all traffic merged and shared the three lanes.
Construction of the Tamar Bridge began in July
1959. Before this, the lowest road crossing of the
River Tamar was
Gunnislake New Bridge at the village of
Gunnislake. This seven-arched
granite bridge was built in the early
16th century (c.
1520). It is still in use today but it is only wide enough to carry one lane of traffic. Before the Tamar Bridge was opened, most car drivers wishing to travel between
Saltash (on the Cornish side) and the Devon city of
Plymouth used
car ferries. Today the Tamar Bridge carries approximately 40 000 vehicles every day. It is co-owned by Plymouth City Council and Cornwall County Council, and is managed by the Tamar Bridge and
Torpoint Ferry Joint Committee. A
toll of
GBP1.00 per car is charged when driving from Cornwall into Devon.
The Tamar Bridge is located above the
Hamoaze, and runs parallel to
Isambard Kingdom Brunel's
Royal Albert Bridge (usually simply referred to as
Brunel Bridge) which opened in
1859 and is considered to be one of his greatest railway achievements. Both bridges offer wonderful views of the
Tamar Valley and
Tamar Estuary. The Tamar,
Lynher and
Tavy Valleys form one of England's thirty-seven
Areas of Outstanding Natural Beauty.
 |
Panorama of the Royal Albert Bridge and the Tamar Bridge |
Why it was needed
In the
1950s (and for centuries before this) road users wishing to drive from Saltash to Plymouth had two main choices. They could take a long detour north either to Gunnislake New Bridge (a one-lane medieval bridge), or even further north to the land-link between Devon and Cornwall. Or they could cross the river by ferry. For centuries there was a ferry link between the two counties just downstream from the current bridge, but the ferries did not have sufficient capacity to transport large numbers of vehicles.
After failing to secure
government funding for a new road bridge, Plymouth City Council and Cornwall County Council applied for permission to operate a toll bridge for which they received Royal assent in
1957.
Construction
The Tamar Bridge was the first major
suspension bridge to be constructed in the
UK after the
Second World War. It was also the longest suspension bridge in the UK at that time. Its central span measures 335m (1100ft).
The bridge was constructed by Cleveland Bridge and Engineering Company, and building work began in July
1959. It had a
concrete deck, and was capable of carrying
lorries up to 38
tonnes. The construction cost over
GBP1.5 million, and the bridge opened to traffic in October
1961. H.M. Queen Elizabeth,
The Queen Mother officially opened the bridge on
April 26 1962.
Tamar Bridge in use
The bridge was three lanes wide (until
2001, see below). Local traffic had to merge with traffic from the
A38 trunk road, which runs from
Bodmin in
Cornwall to
Mansfield in
Nottinghamshire (approximately 300 miles (490km)). The point at which the two streams of traffic merged to cross the bridge into Devon was a notorious
accident black spot.
In
1961, approximately 4000 vehicles used the Tamar Bridge each day. This had dramatically increased by
1990s. In
1998 the
hourly rate during the morning rush hour was 2500 vehicles. The average weekday saw 38 200 vehicles cross the bridge and the summer weekday flow was even higher at 42 900 (the Tamar Bridge is an important
tourist route into Cornwall). In contrast, the
Torpoint ferry link could transport a maximum of 300 vehicles per hour. (See [
1]) The Torpoint Ferries operate between the Cornish town of
Torpoint and the Devon city of
Plymouth; this is more southerly crossing than the Tamar Bridge, linking Torpoint and the
Rame Peninsula to Devon. As such it is not in competition with the Tamar Bridge, in fact the Tamar Bridge and
Torpoint Ferry Joint Committee manage the bridge, and revenue from its tolls subsidise the Torpoint ferries.
Why this was necessary
 |
Close-up of the cantilever platforms being added to the Tamar Bridge during the strengthening and widening project, 1999 |
In the late
1990s, after nearly four decades of use, it was found that the Tamar Bridge would not be able to meet a new
European Union directive that bridges should be capable of carrying
lorries up to 40
tonnes. In fact, the
concrete deck had deteriorated so much that the weight limit for vehicles crossing bridge was in danger of being reduced to 17 tonnes. It was agreed that this restriction would damage the local
economy, so the bridge needed to be strengthened or replaced.
It was estimated that building an alternative river crossing would cost in excess of
GBP300 million. Once a viable strengthening scheme was proposed, the idea of building a new bridge was abandoned due to the high cost.
The main problem with strengthening the Tamar Bridge was that since it catered for around 40 000 vehicles a week, closing it for the duration was not a viable option. An
engineer proposed temporarily adding
cantilever platforms to the sides of the bridge to accommodate traffic while the main deck was strengthened. Once this revolutionary technique had been accepted, it was soon decided that these two extra lanes should be permanent additions to the bridge in order to increase the number of lanes from three to five.
This additional capacity was not expected to encourage a large increase in the number of vehicles using the Tamar Bridge. The
A38 passes through the three-lane
Saltash Tunnel on the Cornish side of the bridge (this acts as a
bypass for Saltash and opened in
1988). The tunnel was expected to regulate the amount of traffic using the bridge despite the increased capacity. The real benefit of these extra lanes would be to make the Tamar Bridge safer and more pleasant for all types of traffic. Pedestrians and cyclists would be safer since they were properly separated from all motor vehicles. Also, local traffic eastbound from Saltash would no longer have to merge with the
A38, eliminating a notorious
accident black spot.
Progress of the project
The principal designer of the strengthening and widening of the Tamar Bridge was Hyder Consulting Ltd, and the principal contractor was Cleveland Bridge UK Ltd (who originally built the bridge). The overall cost was approximately
GBP34 million (a fraction of the estimated
GBP300 million for a new bridge). This was funded from the revenue from tolls paid to cross the Tamar Bridge into Devon.
Work began on the Tamar Bridge in March
1999 and was completed, one month behind schedule, in December
2001. At one point the project was three months behind schedule. The delays were due both to an embargo on road works for the total
solar eclipse of
August 11 1999 which saw tourists flock to Cornwall, one of the few areas of the UK in the path of totality, and also due to extremely bad weather during the winter of 1999/2000.
The improved bridge was fully opened to traffic on
December 20 2001 (although it was never fully closed, in fact during peak hours every effort was made to keep three lanes open). The Tamar Bridge was officially reopened by
Princess Anne on
April 26 2002—forty years to the day after it was first officially opened.
How it was strengthened and widened
The Tamar Bridge originally had a
concrete deck. This had degraded so seriously over its four decades of use that rather than simply being reinforced it was entirely replaced by an
orthotropic steel deck (i.e. a deck formed from steel plates supported underneath by longitudinal ribs or stiffeners). The members were also strengthened by the addition of steelwork, and 18 new diagonal
cable stays were fitted. The two new
cantilever lanes were added to the bridge before the old concrete deck was replaced so as to be available to diverted traffic. At all times during the project, the importance of maintaining the flow of traffic over the bridge was emphasised. Even during construction work the Tamar Bridge served approximately 40 000 vehicles a week.
When modifying
suspension bridges engineers have to be constantly aware of the distribution of weight. At first, steel may sound like an unlikely choice of construction material for the replacement deck, especially since the bridge will have to support five lanes of steel deck instead of the original three of concrete. However, even with the replacement steel deck and the addition of two
cantilever lanes, the new bridge weighs only 25
tonnes more than the original.
The new steel deck is formed from 82 orthotropic panels. Each panel weighs 20
tonnes, and measures 15m by 6m (approximately 49ft by 20ft). They were constructed in
Darlington,
County Durham by Cleveland Bridge UK Ltd and driven nearly 400 miles (over 600km) to the Tamar Bridge and welded together on site.
Worldwide recognition
The Tamar Bridge is the world's first
suspension bridge to be widened using
cantilevers, and the world's first bridge to be widened and strengthened while remaining open to traffic. This innovative engineering project has received many awards and its place in the annals of engineering is assured.
The Tamar Bridge strengthening and widening project was:
*the winner of the highly prestigious
British Construction Industry Civil Engineering Award for 2002 [
2]. The
BCIAs are widely considered to be one of the highest honours in the industry.
*the winner of the Historic Structures category (30 years or older) of the Institution of Civil Engineers Awards 2002 [
3]
*one of eight finalists for the
Prime Minister's Better Public Building Award 2002 [
4].
Engineers from around the world have been interested in the project. For example,
Bill Moreau, the chief engineer for the
New York State Bridge Authority USA, has visited the newly reopened Tamar Bridge to examine the project with a view to adapting it for some of
New York's aging stock of suspension bridges.
As a recognisable symbol of the local area, as well as the main road connection between
Cornwall and the rest of
England and the
UK, the Tamar Bridge is often used for a focus for
protests or
charity events.
Local
commercial radio station
Pirate FM (named for the history of sea
pirates, it's not an illegal
pirate radio station) held a charity fundraiser in April
2002, which involved redecorating the newly reopened Tamar Bridge. They hung a 563m (1848 ft) clothesline along the entire span of the bridge, and decked it out with 1000 pairs of underwear including knickers, panties, bloomers and thongs.
In March
1998, after the closure of
Europe's last
tin mine South Crofty in Cornwall (which has since reopened), campaigners trying to raise the profile of Cornwall's economic crisis encouraged commuters to pay the
£1.00 toll in
pennies. Since the bridge serves 2500 vehicles an hour in peak times, any scheme that slows down the process of paying tolls is likely to cause long tailbacks and make the news.
On
January 23 2004, four protesters climbed onto the gantry over the Tamar Bridge to highlight the work of the group
Fathers 4 Justice who promote the rights of fathers in
custody disputes. Similar protests for male custody rights in
2004 have also taken place on cranes next to
Exeter Crown Court (in
Devon) and at next to
Tower Bridge,
London.
The bridge has unusually become such a cultural focus for its surrounding areas, including Plymouth and parts of Cornwall, that references to the bridge have often found their way into local expressions. Indeed, references to bridges in Plymouth circle almost exclusively around the bridge itself. The site has, over the years, become a focal point of many wishing to end their own life, possibly due to the fact that the bridge covers an isolated part of the 6km long Wolseley Road and the
River Tamar itself, making bodies difficult to find. Many expressions, for example, "Go jump in the Tamar!" as a euphemism for "Go away!", have developed around this.
* The images in this article were taken by
Tony Tapp and are used with permission
*
Google image search for Tamar Bridge*
Plymouth City Council*
Cornwall County Council*
Official Tamar Bridge website*
Official Torpoint Ferry website*
The Tamar Bridge Act 1998*
From the Select Committee on the Tamar Bridge Bill (widening and strengthening)
*
Hyder Consulting Ltd*
Cleveland Bridge Ltd*
The British Construction Industry Awards*
Institution of Civil Engineers*
Better Public Building Awards
